[Help with Starter Change]

so, I've been doing every single monotype run in rejuvenation but now I'm in a bit of a dificult spot. I know that even in the easiest dificulty a mono steel run will be impossible if I choose piplup as a starter (because I literally can't get steel types prior to the first gym and even if I did I'd get stuck on the 2nd gym) so I've made the executive decision to pretend like riolu is still available as a starter and replace my starter with it! here's the thing tho, I'm pretty stupid and as a stupid person will tell you doing anything that requires any kind of braincell usage is very hard therefore I need help with changing my starter... just tell me what program I should use and I'm sure I'll somehow manage!

[Where do I go next? [REJUVENATION]]

melia fought in the library, got tpd to the past and spoke to narcy, now I'm in the present and don't know how to go back to the past, help? :c